Flow control valves for liquid and gas come in many shape and sizes, and are made of a wide variety of materials depending on their intended use.
Typically, flow control valves such as butterfly valves and gate valves are used to control flow of fluid by moving a mechanical member into and out of the flow path to partially or completely block the flow path. Other types of valves, for example roller clamps used in medical intravenous apparatus, control flow by pinching the plastic tubing through which the fluid flows. Still other types of valves operate by controlling the length of the flow path, and therefore the resistance to flow, through the valve.
Despite the wide variety of valves that have been known or used heretofore, there is a continuing need for improved flow control valves that have cost, ease of use, functional, and other advantages compared to prior flow control valves.